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[Xen-devel] Re: xenconsoled CPU denial of service problem

On Wed, Oct 04, 2006 at 12:52:52PM -0500, Anthony Liguori wrote:
> Daniel P. Berrange wrote:
> >On Wed, Oct 04, 2006 at 11:49:56AM -0500, Anthony Liguori wrote:
> >  
> >>Considering that today in Xen we have a default buffer size, it seems 
> >>considerably easier to me to just get rid of xenconsoled completely and 
> >>expand the domU-kernel ring queue to be the actual size of what we're 
> >>buffering today.
> >>
> >>This eliminates all of these problems and gets rid of a dom0 daemon. 
> >>Plus, the domU gets taxed for the buffer memory instead of dom0.
> >>
> >>We would then change xenconsole to read the buffer directly.
> >>    
> >
> >Its very useful to be able to expose the data as a Psuedo-TTY, as
> >it lets people use standard toolset for dealing the DomU log data.
> >eg virt-manager can just connect up a VTE terminal widget straight
> >to the TTY for a terminal UI. Or tools like ttywatch can log the
> >data to file, or network, etc. Or minicom for a standard text based
> >interactive client, etc Forcing everything to use the custom
> >xenconsole client program would be a step backward.
> >  
> Xenconsole could still spit out on a PTY.  You don't necessarily need a 
> daemon though (you could launch a xenconsole for each domain that was 
> started).

The xenconsole would still need the rate-limiting, and once you're launching
one xenconsole per domain, where's the gain over the single xenconsoled
process ? 

> That also gives you a bit more choice in how you expose the console (you 
> could have a xenconsole that spit out via TCP).

Given a TTY, there are already tools which can do this & more. So I don't see
any point in writing such functionality again for Xen. If using HVM domains
one would already typically be exposing a serial console from the guest via
a pseudo-TTY, so doing all PV console stuff via a TTY gives parity in the
management toolset.

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